Copper Immersion Plating on Iron from Copper Sulfate Solutions

The Case in the Absence of Complexing Agents

Abstract

Experiments were carried out to find the mechanism of galvanic displacement: Fe+Cu²⁺→Fe²⁺+Cu. When iron is immersed in a concentrated copper sulfate solution, e.g., 0.5M, a poorly adherent copper is deposited. In this case FeSO₄ or Fe₂O₃ coprecipitated with the copper because the concentration of Fe²⁺ near the interface increased rapidly immediately after the immersion. However, atyell adherent copper was deposited by immersion in an acidic dilute copper sulfate solution, e.g., 0.01M, pH 1.5. In this case the rate of copper deposition, namely, the rate of formation of Fe²⁺ was slow, so that the Fe²⁺ was permitted to diffuse into the bulk of the solution without precipitating, which was the case of well adherent copper plate. The formulation of immersion plating of copper on iron was: CuSO₄ 0.0025-0.03M, pH<2.5, room temperature, immersion time 0.5-15min. The copper plating applied under these conditions was adherent to iron, hence copper could be electroplated on it from the ordinary pyrophosphate baths.